title: Polyamines are critical for the induction of the glutamate decarboxylase-dependent acid resistance system in Escherichia coli.
abstract: As part of our studies on the biological functions of polyamines, we have used a mutant of Escherichia coli that lacks all the genes for polyamine biosynthesis for a global transcriptional analysis on the effect of added polyamines. The most striking early response to the polyamine addition is the increased expression of the genes for the glutamate-dependent acid resistance system (GDAR) that is important for the survival of the bacteria when passing through the acid environment of the stomach. Not only were the two genes for glutamate decarboxylases (gadA and gadB) and the gene for glutamate-γ-aminobutyrate antiporter (gadC) induced by the polyamine addition, but the various genes involved in the regulation of this system were also induced. We confirmed the importance of polyamines for the induction of the GDAR system by direct measurement of glutamate decarboxylase activity and acid survival. The effect of deletions of the regulatory genes on the GDAR system and the effects of overproduction of two of these genes were also studied. Strikingly, overproduction of the alternative σ factor rpoS and of the regulatory gene gadE resulted in very high levels of glutamate decarboxylase and almost complete protection against acid stress even in the absence of any polyamines. Thus, these data show that a major function of polyamines in E. coli is protection against acid stress by increasing the synthesis of glutamate decarboxylase, presumably by increasing the levels of the rpoS and gadE regulators.
authors.affiliation: Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892. Electronic address: manasc@intra.niddk.nih.gov.
authors.forename: Manas K
authors.initials: MK
authors.lastname: Chattopadhyay
authors.affiliation: Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Herbert
authors.initials: H
authors.lastname: Tabor
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015317:Biogenic Polyamines / Q000378:metabolism / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D015317:Biogenic Polyamines; D029968:Escherichia coli Proteins; C491226:GadC protein, E coli; C479562:GadE protein, E coli; D008565:Membrane Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C069567:sigma factor KatF protein, Bacteria; D018698:Glutamic Acid; C121044:gadA protein, E coli; C584507:gadB protein, E coli; D005968:Glutamate Decarboxylase
keywords: Bacteria; Cyclic AMP (cAMP); Decarboxylase; Gene Expression; Glutamate; Microarray; Polyamines; Putrescine; Spermidine